Immunotherapy has transformed the treatment of several cancers — but its side effects work in a fundamentally different way from chemotherapy, and understanding that difference is important for anyone starting treatment. This guide explains how immunotherapy side effects differ, what to watch for, and why they are managed differently.
Why the side effects are different
Chemotherapy attacks rapidly dividing cells, so its side effects — hair loss, low blood counts, nausea — come from that. Immunotherapy works by activating your own immune system against the cancer. Its side effects come from a different source: an over-active immune system that can occasionally start attacking healthy organs too.
These are called immune-related side effects, and they can affect almost any part of the body — skin, gut, thyroid and other hormone glands, liver, and lungs, among others.
What to watch for
Immune-related effects can be mild or, less commonly, serious, and they can appear even after treatment has finished. Tell your team promptly about:
- Diarrhoea or more frequent stools, or blood/mucus in the stool
- A new or worsening skin rash or itching
- Persistent tiredness, feeling cold, or unusual weight change (thyroid/hormone effects)
- Shortness of breath or a new cough
- Yellowing of the eyes, or unusual tummy pain (liver)
- Severe headache, dizziness or vision changes
With immunotherapy, an ordinary-sounding symptom like persistent diarrhoea can matter more than it would on chemotherapy — because it can signal the immune system acting against healthy tissue. Report early; early treatment works best.
The key message: report immune-related symptoms early. Caught early, most are very manageable — often with medicines that calm the immune response. Left unreported, a few can become serious. Early communication is genuinely the safest thing you can do.
How immunotherapy side effects are managed
Management is different from chemotherapy. Mild effects are often treated with supportive measures; more significant ones with medicines that dampen the immune response, and sometimes a pause in treatment. This is why your team monitors blood tests — including thyroid, liver and other markers — during immunotherapy, and why you should carry a card or note saying you are on it, so any doctor you see knows. Whether given in a day-care setting or otherwise, the monitoring is part of safe treatment.
Frequently asked questions
Are immunotherapy side effects worse than chemotherapy?
Not necessarily — many people tolerate immunotherapy well. They are simply different, and a few can be serious if not reported early.
Can side effects appear after treatment ends?
Yes. Immune-related effects can develop weeks or even months later, so keep reporting new symptoms even after finishing.
Should I take an anti-diarrhoeal for loose motions on immunotherapy?
Call your team first. Diarrhoea on immunotherapy can be immune-related and is managed differently from ordinary diarrhoea.
Is immunotherapy right for me?
It depends on your cancer type and biomarker results. A specialist review can confirm suitability.
Related reading: Immunotherapy · Chemotherapy · Targeted Therapy · Day Care Chemotherapy · Patient Support
Reviewed by Dr. Harish Kancharla
DM (Medical Oncology), AIIMS, New Delhi · MD (Internal Medicine), PGIMER, Chandigarh
Senior Consultant – Medical Oncology & Hemato-Oncology, Yashoda Hospitals, Somajiguda, Hyderabad
Telangana State Medical Council Registration No. 77186
Last reviewed: August 2026
This article is general information, not personal medical advice. Cancer decisions depend on your individual diagnosis, stage, test results and overall health. Please see our Medical Disclaimer.